Occurrence of a new hematoside in the kidney of guinea pig

9-O Acetylated Gangliosides in Health and Disease

Glycosphingolipids comprise a lipid class characterized by the presence of sugar moieties attached to a ceramide backbone. The role of glycosphingolipids in pathophysiology has gained relevance in recent years in parallel with the development of analytical technologies. Within this vast family of molecules, gangliosides modified by acetylation represent a minority. Described for the first time in the 1980s, their relation to pathologies has resulted in increased interest in their function in normal and diseased cells. This review presents the state of the art on 9-O acetylated gangliosides and their link to cellular disorders.

The Structural Diversity of Natural Glycosphingolipids (GSLs)

Glycosphingolipids (GSLs) are a subclass of glycolipids made of a glycan and a ceramide that, in turn, is composed of a sphingoid base moiety and a fatty acyl group. GSLs represent the vast majority of glycolipids in eukaryotes, and as an essential component of the cell membrane, they play an important role in many biological and pathological processes. Therefore, they are useful targets for the development of novel diagnostic and therapeutic methods for human diseases. Since sphingosine was first described by J. L. Thudichum in 1884, several hundred GSL species, not including their diverse lipid forms that can further amplify the number of individual GSLs by many folds, have been isolated from natural sources and structurally characterized. This review tries to provide a comprehensive survey of the major GSL species, especially those with distinct glycan structures and modification patterns, and the ceramides with unique modifications of the lipid chains, that have been discovered to date. In particular, this review is focused on GSLs from eukaryotic species. This review has listed 251 GSL glycans with different linkages, 127 glycans with unique modifications, 46 sphingoids, and 43 fatty acyl groups. It should be helpful for scientists who are interested in GSLs, from isolation and structural analyses to chemical and enzymatic syntheses, as well as their biological studies and applications.

Exploration of the Sialic Acid World

Sialic acids are cytoprotectors, mainly localized on the surface of cell membranes with multiple and outstanding cell biological functions. The history of their structural analysis, occurrence, and functions is fascinating and described in this review. Reports from different researchers on apparently similar substances from a variety of biological materials led to the identification of a 9-carbon monosaccharide, which in 1957 was designated "sialic acid." The most frequently occurring member of the sialic acid family is N-acetylneuraminic acid, followed by N-glycolylneuraminic acid and O-acetylated derivatives, and up to now over about 80 neuraminic acid derivatives have been described. They appeared first in the animal kingdom, ranging from echinoderms up to higher animals, in many microorganisms, and are also expressed in insects, but are absent in higher plants. Sialic acids are masks and ligands and play as such dual roles in biology. Their involvement in immunology and tumor biology, as well as in hereditary diseases, cannot be underestimated. N-Glycolylneuraminic acid is very special, as this sugar cannot be expressed by humans, but is a xenoantigen with pathogenetic potential. Sialidases (neuraminidases), which liberate sialic acids from cellular compounds, had been known from very early on from studies with influenza viruses. Sialyltransferases, which are responsible for the sialylation of glycans and elongation of polysialic acids, are studied because of their significance in development and, for instance, in cancer. As more information about the functions in health and disease is acquired, the use of sialic acids in the treatment of diseases is also envisaged.

Structural characterization of gangliosides isolated from mullet milt using electrospray ionization-tandem mass spectrometry

Electrospray ionization (ESI) coupled with tandem mass spectrometry has been used in conjunction with microwave-mediated saponification, periodate oxidation, and clostridial sialidase hydrolysis to enable detailed structural characterization of gangliosides and their derivatives present in mullet milt. The gangliosides extracted from mullet milt were determined to be GM3, GM3 lactone, GM3 methyl ester, and 9-O-acetyl GM3. For the major ganglioside GM3 and all GM3 derivatives, the ceramide composition was revealed to be C18:1/C16:0. GM3 with a C18:0/C16:0 ceramide was also found as a minor ganglioside. Both the ganglioside intramolecular ester and the ganglioside methyl ester (lacking carboxylic acid groups) showed dominant chloride attachment peaks (M + Cl)- in negative ion ESI-MS in addition to low intensity peaks corresponding to (M-H)-. GM3 and O-acetyl GM3 bearing carboxylic acid functions showed only (M-H)-. In positive ion ESI, GM3 and O-acetyl GM3 revealed (M + 2Na-H)+ peaks in addition to (M + Na)+, indicating free exchange of the carboxylic acid proton with a sodium cation, while the ganglioside intramolecular ester and ganglioside methyl ester with no acidic protons yielded only (M + Na)+. The strategy of employing ESI-MS to detect products of established wet chemical reactions represents a general approach for elucidation of ganglioside structural details.

Detection of 4-O-acetyl-N-glycolylneuraminyl lactosylceramide as one of tumor-associated antigens in human colon cancer tissues by specific antibody

Antibody to 4-O-acetyl-N-glycolylneuraminyl lactosylceramide [GM3(Neu4AcGc)] was prepared by immunizing chicken with the glycosphingolipid antigen. The specific antibody was purified by affinity chromatography columns of Octyl-Sepharose linked to the homologous immunogen and its deacetylated analogue [N-glycolylneuraminyl lactosylceramide, GM3(NeuGc)], respectively. The specificity of the purified antibody was confirmed by enzyme-linked immunosorbent assay (ELISA) and inhibition of equine erythrocyte hemagglutination using authentic glycosphingolipids as antigens. The results indicated that the antibody recognized both 4-O-acetyl and N-glycolyl groups of terminal sialic acid residue as the immunodeterminants. The purified specific antibody was applied in the confirmation of the presence of GM3(Neu4AcGc) in ganglioside fractions of human colon cancer tissues, which were suspected to have this antigen by studies of alkaline, periodate or neuraminidase treatment [Higashi et al. (1985) Cancer Res. 45, 3796-3802.], by thin-layer chromatography (TLC)-immunostaining technique.